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Full text of "The Flow Of Gases In Furnaces"

CONTINUOUS  OR MULTIPLE  CHAMBER KILNS         117

All of these defects are due to a disregard of the principles which
govern the subdivision of currents of gases when heating or
cooling.

This may be clearly shown by the consideration of a simple case
(Fig. 91), where A is the portion of the tunnel chamber in which
the air is preheated, B the portion of the chamber in which the fuel
is introduced and where the ware is burned, C the portion of the
chamber in which the ware is preheated by the waste heat, E the
flue connection to the chimney and D the portion in which the
ware is being set.

The sections may be considered in order, starting with section
B of the tunnel, where combustion takes place and the ware is
burned. The gas circulation which is to be established in this
section must be such that the hot gases flow to all parts of the
tunnel chamber being heated. The hot gases, however, imme-

_A

t max.



______^ Flow of products of combustion               7j7
,>. Plow of air
FIG. 91.
diately rise to the roof of the tunnel and then flow to where the
cooling gases are drawn down into the waste-gas flue. The
placing of the waste-gas flue under the hearth of the tunnel is,
in general, favorable to the circulation of the heated gases, as it
apparently works upon the downdraft principle. Nevertheless,
it is not possible to obtain a uniform burn to the ware at the
bottom and the top of the turanel chamber. The upper part of
the tunnel is filled with a stream of light gases, the superheated
products of combustion, having a high temperature tfmax, while the
hearth of the tunnel is traversed by a current of waste gases which
are heavier and at a lower temperature W. In order that the
difference between the temperatures £max and tmm shall be as small
as possible it is necessary to set the ware to be burned in a compact
checker which will increase the resistance to the flow of the gases
in the upper part of the setting and to decrease the resistance to